1. Field of the Invention
The present invention relates to cheese analogs produced by using combinations of rennet casein and isoelectric casein. These products are not always readily available, and it would be advantageous to be able to use combinations of them in the preparation of cheese analogs. In the past it has always been thought necessary to use either one of these materials or the other, exclusively, because they are not compatible with each other.
2. Background
Casein is a by-product of the dairy industry and is usually prepared from skim milk. There are several methods for isolating casein from milk. The physical properties and chemical composition of the casein obtained depend upon the source of the milk and its quality, and upon the method of preparation of the casein.
There are two principal methods for producing casein from milk. These are acid precipitation of casein at its isoelectric point, which is about pH 4.7, and enzyme coagulation by the action of rennin or other suitable enzyme.
Ideally, casein, no matter how produced, would be tasteless, odorless, and noncrystalline. In fact, isoelectric casein produced by acid precipitation may have an objectionable taste and mouthfeel. A number of techniques have been devised, therefore, for treating isoelectric casein (hereafter, acid casein) in order to improve its properties to make it suitable for use in the production of cheese analogs.
Rennet casein is often preferred to isoelectric casein for many food uses because of its bland flavor.
3. Description of the Prior Art
The Bell et al. U.S. Pat. No. 3,922,374, describes a process for making a cheese analog from raw materials including acid casein and fat. In this process, finely divided acid casein was mixed with an aqueous solution of acid, then high shear was applied while calcium hydroxide was added. The resulting calcium caseinate was mixed with fat and other conventional cheese analog ingredients, still using high shear mixing and subatmospheric pressure, to form a cheese analog blend. Rennet casein could not be used in this process, as either a partial or complete replacement for the acid casein, because it would not be solubilized by this kind of processing.
The Middleton U.S. Pat. No. 4,197,322, describes a somewhat different process for producing a cheese analog. In the Middleton process, acid casein was solubilized at a pH above 7.0, and subsequently reprecipitated by acidification, to produce a wet calcium caseinate curd. The curd was then blended with oil and other cheese analog ingredients to form the cheese analog product. As was the case with the Bell et al. process, the Middleton et al. process cannot be used successfully with rennet casein. In addition, the Middleton et al. process requires a curd-forming step, which entails additional labor and processing costs as compared to the Bell et al. process.
Rennet casein has better flavor and flavor retention characteristics than acid casein, and it is only natural that it has been tried for use in the producttion of cheese analogs. In German Pat. No. 2,808,303, Bixby et al. disclose a process that requires the use of cheese melting salts to solvate rennet casein in water, at or above a threshold temperature. It would not be possible to use a combination of acid casein and rennet casein in the Bixby et al. process, because the acidic nature of the acid casein would interfere with the solvation of the rennet casein, so that an acceptable cheese analog could not be produced.